1. Field of the Invention
This invention relates to a hydraulic pressure apparatus having an open port at an inner peripheral surface of a cylinder and a brake pressure control apparatus using the hydraulic pressure apparatus.
2. Discussion of the Related Art
As a hydraulic pressure apparatus of the type above, an accumulator, which is used in a hydraulic pressure brake system (for example, the accumulator disclosed in JP2001-328526 A), has been known. According to this accumulator, a cylinder bore is provided in a housing body and a piston is slidably disposed in the cylinder bore. An accumulator chamber is formed between one side of the piston and the cylinder bore.
On the other hand, the other side of the piston, which is located opposite to the accumulator chamber, is provided with a spring chamber, into which the atmospheric pressure is introduced through a passage formed on the housing body. The piston is always biased towards the accumulator chamber side by a spring provided in the spring chamber. The spring chamber, into which the atmospheric pressure is introduced, is in communication with the passage through a fine bore.
The fine bore is formed by punching out an inner peripheral surface of the spring chamber with a punch having a curved surface at the root of a punching portion. An opening portion of the fine bore to the spring chamber is formed with the curved surface (chamfered surface) around the opening portion by transferring the curved surface shape of the punch to the opening portion at the same time the fine bore is formed. According to this method, no burr is formed at the opening portion to the spring chamber and any damage to a sealing member can be prevented by smoothly passing the same over through the opening portion upon assembling the piston into the cylinder bore.
Further, a burr removing technology is disclosed, for example, in JP2005-212035 A when any burr is generated at the opening portion of the machined bore. JP2005-212035 A discloses a burr removing tool having an operating shaft, a grip for holding formed on one end of the shaft and a blade member pivotally mounted on the other end of the shaft at a pivotal point. The blade member is formed with a tapered blade portion on a rotation shaft having a predetermined length.
According to the burr removing tool disclosed in JP2005-212035A, the burr at the opening portion is removed by rotating the pivotal point around the center of opening portion with pressing or pushing the tapered blade portion against the opening portion. Thus the blade portion is rotated along the opening portion to remove the burr which has been generated at the opening portion.
According to the accumulator disclosed in JP2001-328526 A, if the inner diameter of the fine bore is equal to or less than a predetermined value, the possible damage of the sealing member can be reduced upon inserting the sealing member into the cylinder bore. This is a certain advantage achieved by the effect of the curved surface formed on the opening portion. However, if the diameter of the opening formed at the inner peripheral surface of the spring chamber is larger than the predetermined value, the sealing member made of a rubber material may enter into the inside of the opening and not so much effects were proved regarding the prevention of damage to the sealing member.
Removing the burr at the opening potion with the burr removing tool disclosed in JP2005-212035 A, requires an extra time or man-hour for removing the burrs, and is not sufficient to make the shape of the opening portion as to prevent the damage of the sealing member. Further, it takes much time or man-hour to remove the burrs dropped from the opening portion into the housing body. This was not an effective way to trim the shape of the opening portion.